Catadioptric telephoto systems



SEARCH ROOM Feb. 15, 1955 F. G. BACK ETAL cATADIoPTRIc TELEPHoTo SYSTEMS 3 Sheets-Sheet l Filed Nov. 25, 1953 na.. C J A, .1Q W35 F. G. BACK ETAL CATADIOPTRIC TELEPHOTO SYSTEMS Feb. -15, 1955 3 Sheets-Sheet 2 Filed NOV. 25, 1953 Feb- 15, 1955 F. G. BACK ETAL CATADIOPTRIC TELEFHOTO SYSTEMS 3 Sheets-Sheet 3 Filed Nov. 25, 1953 .ooonsmc :UE 222.53.

INVENTOR.

FRANK G. BACK HERBERT LOWEN 2,701,983 Patented Feb. 15, 1955 is formed upon the rear center portion of the convex side of the correction plate the secondary convex mirror 12 therefore has the same radius of curvature as this convex side of the correction plate 10. The secondary C ATADIOPTRIC TELEPHOT() SYSTEMS 5 convex mirror 12 reliects the rays impinged thereon in such manner that they pass through the negative rear ele- Frank G. Back and Herbert Lowen, Glen Cove, N. Y.; ment constituted by lens systems 13, 14 and 15 (a nonsaid Lowen assignor to said Back cemented triplet) or the lenses 18 and 19 and 20 and 21 which respectively constitute non-cemented doublets em- Allhcmlm November 25 1953 Sena! N 394,398 10 ployed as negative rear elements in the herein illustrated lim" three embodiments of the present invention. The rays 5 Cl (Cl' sil- 57) passing throughv the negative rear element pass from thence through the aperture 16 provided in the center of the primary concave spherical mirror 1l to the focal The present invention relates to optical systems and plane 17. in particular to catadioptric telephoto. systems for still Preferred forms of the present invention are illustrated cameras, motion picture cameras, television cameras and in the accompanying drawings, in which: all such devices -in which objectives with very long focal Fig. l is a schematic cross-sectional view of one emlengths are required. bodiment of the present invention illustrating a lens of It is an object of the present invention to provide objec- 20 150" equivalent focal length. tives which possess very long equivalent focal length in Fig. 2 is a view like Fig. l illustrating another embodicombination with relatively short length and light weight merit constituting a modification of a construction in acconstruction and which display also a high degree of cordance with the present invention accomplished by the correction for all aberrations over the entire field. replacement of the negative rear element and illustrating It is a further object of the present invention to provide a lens of 80" equivalent focal length. a novel construction for teleobjectives in which the posi- Fig. 3 is a view like Fig. l illustrating a lens of 40" tive front element is replaced by an arrangement of equivalent focal length. spherical mirrors. Fig. 4 is a table of data as they apply to the telephoto Conventional telephoto lenses consist of a positive front system illustrated in Fig. l. element in combination with a negative rear element. Fig. 5 is a table of data as they apply to the telephoto To satisfy the requirements of extremely long focal system illustrated in Fig. 2; and length, conventional lenses of necessity were required to Fig. 6 is a table of data as they apply to the telephoto have a substantial length. By means of the present invensystem illustrated in Fig. 3. v tion a novel construction for teleobjectives is provided in Having now reference to the drawings it will be seen which the physical dimensions of the lens are substanthat Fig. 1 represents a catadioptric telephoto system tially reduced so that the necessity for long unwieldy which has an equivalent focal length of 150". The anequipment is eliminated while the requirements for very nular entrance pupil of the system corresponds to a speed long focal length are satisfactorily met. The mirror of F :25. The values for the components are as follows:

Lens Glass Radii Thickness Separation Corrector Plate 10, Secondary BSC Ri=-65.354

Mirror 12 ND= 1. 517 t1=.e74"

V=4.5 R,+6o.479"

81=11.5" DBC Ri= 2693" Negative Rear Element 13 Nox 1. 611 ti=.150

i== .160" LF Rt=+ 4.238" Negative Rear Element 14 Nn= 1. 5795 t3=. 250" s.= .175" DBC Rs=Inf. Negative Rear Element l5 Nn= 1. 611 4=.150

V=58.8 R|= 3.681" Prim Min-o 1i R se soo" s 5'210" l' To Fggl Plane y s 31=12- 790" Equivalent focal length 150.00. Equivalent relative aperture Fz25, BSO-boro silicate crown. DBC-dense barium crown. LF-light flint.

Nia-index oi refraction for sodium light 5893 V-Abbes dispersion number.

arrangement of the present invention permits a reduction in size of the equipment due to the employment of a folded light path.

To illustrate the present invention reference is had to Fig. l and it will be seen that the image forming axial parallel rays pass from the object through the substantially powerless correction plate 10 and are impinged on the spherical concave primary mirror 11 which reects these rays on to the secondary convex mirror 12 which A further modification of the present invention is illustrated in Fig. 2 in which a system with an 80 equivalent focal length having an equivalent relative aperture of Fzl5 is illustrated.

The construction here below set forth shows an alternate adaption and modification of the present invention as illustrated in Fig. l in` which a non-cemented doublet is employed as a negative rear element whereas in Fig. 1 an arrangement having as a negative rear element a noncemented triplet was shown. The values for the 80" equivalent focal length F: system are as follows:

preferred forms of construction embodying the present invention have been set forth.

No-index of refraction for sodium light 5893 V-Abbee dispersion number.

Having now reference to Fig. 3 it will be seen that a further adaptation and modification of the present invention is illustrated wherein a catadioptric telephoto system of 40" equivalent focal length and equivalent relative aperture F:8 having a negative system consisting of a non-cemented doublet is constructed in accordance with the present invention. The values for this system are as follows:

Having set forth our invention what we desire to claim and secure by Letters Patent is:

1. A catadioptric telephoto system comprising in combination a positive front system consisting of a substantially powerless meniscus shaped correction plate, a primary concave mirror and a secondary convex mirror and a negative rear system consisting of a non-cemented airseparated plural lens element combination, the concave Lens Glass Radii Thickness Separation Corrector Plate 10b, Secondary BSC Yin-36.979

Mirror 12b Nia-1.517 ti-.700"

V 64.5 Iii-+Mw .1i-8.182" BSG R411.657 Negativo Rear Element 20 ND-L517 til-.200"

M .m' DF 11p-30.433" Negative Rear Element N13-1.621 h-.SW

V -363 Rr+ 9.508"

.lg-3%" Primary Mirror 11b Rg.- 35.512" To Focal Plano u-5.272"

Equivalent focal length 40.00".

Equivalent relative aperatnrs FzB.

BSC-boro silicate crown.

DF-dense int.

NIJ-index of refraction for sodium um saca V-Abbe's dispersion number.

As it will be evident from the foregoing description of three preferred forms of the present invention illustrated in Figs. l, 2, 3, respectively that the positive front element is substituted by an arrangement of mirrors which has good adaptability for use in combination with a selected variety of negative systems and provides due to the specitic charactertistics inherent in mirror arrangements for a high degree of correction relative to aberration over the entire field. This system constituted of a positive front element consisting of an arrangement of mirrors and a negative rear element comprising noncemented doublets and triplets respectively, possesses the distinct advantage of being adaptable to short length and light weight construction. A further aspect of the present invention resides in the fact, that the secondary spherical convex mirror has the same radius of curvature as a convex surface of the correction plate so that the rear center portion of the correction plate can be prepared for use as the secondary spherical convex mirror without requiring special grinding and polishing operations.

It is obvious that various modifications may be made in the choice of elements and their design and selection by those skilled in the art without thereby departing from the scope of the present invention it being understood that for the purpose of illustration and exemplication three face portion of said powerless meniscus shaped correction plate facing the object, the convex rear centered portion thereof provided with a mirrored surface adapted to form the secondary convex spherical mirror of said positive front system, a spherical concave mirror, spaced a predetermined distance behind said correction plate and secondary convex spherical mirror, said concave mirror adapted to reect rays passing through the correction plate upon said convex spherical mirror, a negative auxiliary system positioned in the ray passage between the convex spherical secondary mirror and a central aperture provided within said spherical concave mirror said arrangement adapted to permit light rays to pass from the object through the correction plate to the concave spherical primary mirror from thence to the convex spherical secondary mirror, from thence through the negative rear system and through the aperture in said concave primary mirror onto the lm plane.

2. In a catadioptric telephoto system, in accordance with claim l, the spherical concave primary mirror and the spherical convex secondary mirror adapted to form the positive front system thereof and an uncemented negative lens component comprising a triplet adapted to form 35 the negative rear system thereof.

wherein the equivalent focal length is 80.00;

the equivalent relative aperture is F: and BSC is boro silicate Lens Glass Radil Thickness Separation Corrector Plate 10, Secondary BSC Ri65. 354" Mirror 12 Nn- 1. 517 ti-. 674" 81=11. m" DBC Rw- 2.693" Negative Rear Element 13... Nn= 1. 611 ti=.150"

V =5&8 Rpt-25.046

.h- 160 LF Rs=+ 4. 238" Negative Rear Element 14 Nn- 1. 5795 tw. 250

8|- 175 DBO Rif-Inf. Negative Reet Element 15 Nnl. 511 tw. 150

.94- 5. 210l Primary Mirror 11 Rin-56. 800" To Focal Plane .v5-12. 790" wherein the equivalent focal length 1s 150.00"; the equivalent relative aperture is F: and BSC is crown and DBC is dense barium crown, LF is light flint; and Nn is the index of refraction for and V is Abbes dispersion number: t indicates thickness, s indicates separation and R is the radius of the curvature.

4. In a catadoptric telephoto system in accordance with claim 1 alens arrangement comprising:

boro silicate sodium light 5893 crown and DF is dense int; and Nn is index of refraction for sodium light 5893 and V is Abbes dispersion num- 25 ber; t indicates thickness, s indicates separation and R is the radius of the curvature.

5. In a catadioptric telephoto system in accordance with claim 1 a lens arrangement comprising:

-wherein the equivalent focal length is 40.00"; the equivalent relative aperture is F:8, and BSC is boro silicate crown and DF is dense int; and Nn is index of refraction for sodium light 5893 and V is Abbes dispersion number: t indicates thickness, s indicates separation and R is the radius of the curvature.

Lens Glass Radil Thickness Separation 01mm: No-82511 Iii-"wm" a-.ew'

ve4.5 m+ee47w ,l nso 11p-10.505" "8'888' Negstmnmnkmenus Nn- 1.511 t,.aoo"

v-54.5 11.-- eow' mi N u numemmtio N DF1.521 Bw," uw' s ano" n m n vD-au 1in-11.570" 7867, nmnu --aaaw' mm3: R References Cited in the file of this patent UNITED STATES PATENTS 2,378,301 Kaprelan June 12, 1945 2,413,286 BUChele 1946 2,441,093 Akl 1948 2,504,383 Apl'. 18, 1950 2,576,436 e1' NOV. 27, 1951 2,608,129 Taylor Aug. 26, 1952 2,610,547 Bach Sept. 16, 1952 FOREIGN PATENTS 824,558 Gl'mlny Dec. 13, 1951 

